1. Field of the Invention
The present invention relates to a method for forming a barrier metal layer of semiconductor device.
2. Description of the Prior Art
Generally, a barrier metal layer, which is formed between aluminum and junction, is used to prevent junction breakdown due to metal diffusion.
To form such a barrier metal layer, initially after forming an insulating layer on a silicon wafer having a junction therein, a contact hole is made in the insulating layer by partially etching the insulating layer to expose the junction. Since natural silicon oxide layer will always build up on the surface of the exposed junction, the natural silicon oxide layer should be stripped prior to the formation of the barrier metal layer since it degrades the electric properties of the semiconductor device. In the prior art, wet cleaning process or dry cleaning process using etching gases such as CH.sub.4 /O.sub.2 and NF.sub.3 was used to eliminate the natural silicon oxide layer. This process requires additional equipment as well as demanding much process time since it is not an in-situ type process.
Also as the size of the contact hole becomes smaller as semiconductor device dimension decreases, poor step coverage of the barrier metal layer due to small contact size causes problems in barrier reliability.